This invention relates to medical devices and, more particularly, to medical devices useful in providing brachytherapy.
Brachytherapy is a form of cancer treatment, in which radiation sources placed inside the patient""s body irradiate a tumor. In brachytherapy, a surgeon usually implants several radioactive seeds in or around the tumor, thus providing a higher radiation dose to the tumor than would be possible with external beam radiation therapy. Careful placement of the radioactive seeds allows localized and precise irradiation of the tumor. Because the radiation dose diminishes rapidly outside the radioactive seed, the radiation dose to surrounding healthy tissues is reduced.
Radioactive seeds typically are tiny (usually 1 mm by 4.5 mm), roughly cylindrical objects containing very small amounts of radioactive material. In one widely practiced brachytherapy procedure, the radioactive seeds are implanted permanently inside the patient""s body. The half-life of the radioactive material is generally short, and the radioactivity in the seeds decays after about three to six months to the point that there is little detectable radiation. Two radioactive isotopes commonly used for permanent implants are iodine-125, often used to treat slower growing tumors, and palladium-103, which is preferred when the tumor is fast-growing. Other radioactive materials have been used in implants as well.
Many forms of cancer respond to brachytherapy, including several forms of prostate cancer. Brachytherapy is generally less invasive than surgery, usually results in fewer side effects for the patient than surgery or external beam radiation, allows for a short recovery time and reduces the impact upon the patient""s quality of life.
In brachytherapy treatment, it is common for the physician to implant a large number of seeds in the patient""s tissue. In a typical prostate implantation, for example, eighty to one hundred twenty radioactive seeds may be implanted at varying positions in and around the prostate. The physician uses a device called an applicator to perform the implantation. The applicator usually includes a slender push rod (or stylet) to push the radioactive seeds into a hollow implantation needle. The implantation needle, which is usually coupled to the applicator, penetrates the patient""s body and is used to deliver the seeds to the tumor and the area around the tumor. Typically, the surgeon advances a radioactive seed through the needle to a desired location. To deliver multiple seeds, the surgeon can repeatedly place seeds into the void space created by retracting the needle. In some brachytherapy procedures, several implantation needles may be employed, each needle penetrating the patient at a different site. In such a procedure, a single applicator may be used for all of the implantations, the applicator coupled to each needle in turn. In other brachytherapy procedures, a single applicator and a single needle may be used for implantations at several sites.
Usually the applicator contains a supply of radioactive seeds for implantation. Typically the radioactive seeds are supplied in the form of a cartridge or magazine, which is mated to the applicator. The number of seeds supplied by the cartridge or magazine is usually less than the total number of seeds needed for the brachytherapy procedure. Accordingly, the applicator may need to be resupplied with seeds several times during the procedure. The seed-holding system and techniques described below facilitate the rapid resupply of seeds to an applicator. The seed-holding system provides for a holder, which may be disposable, and a transfer device, which may be reusable. The holder stores the radioactive seeds. Several holders loaded with radioactive seeds may be prepared for a single brachytherapy procedure. The transfer device helps dispense the seeds from the holder, and also provides shielding to the seeds, reducing the risk to medical staff of radiation exposure. When the holder is coupled to the transfer device, the seed-holding system can be mated to an applicator, and radioactive seeds may be dispensed from the holder. When the holder is emptied of seeds, the seed-holding system may be disconnected from the applicator, and the empty holder may be ejected from the transfer device. A fresh, full holder may then be coupled to the transfer device, and the seed-holding system may once again be mated to the applicator. The implantation of seeds may then continue. The resupply of seeds may be completed in a matter of seconds.
In one embodiment, the present invention provides a device, including a holder and a transfer device. The holder, which is configured to receive one or more radioactive seeds, includes two components: a main body and a pusher. Both parts may be made of plastic. The holder is further configured to mate to an applicator, and to dispense seeds from the holder""s distal end. The transfer device, which is configured to engage the holder, is composed of several components, including a housing, an expansive spring and a pusher assembly. The transfer device may further include a shield that can be extended to provide radiation shielding around the holder.
Other advantages, features and embodiments of the invention will become apparent from the following detailed description and from the claims.